Now to the latest as we switch gears on the mortar blast that killed seven marines in a live fire training exercise. Military investigators are now scrambling to figure out what went wrong. Abc's abbie boudreau has the latest. Reporter: What began as a routine nighttime training exercise in the nevada desert monday evening turned into a real-life disaster killing seven marines and injuring eight others. The marines were conducting live fire and maneuver training at about 9:55 p.M. Last night a mortar round exploded in the tube rrp they were launching 60-millimeter mortars when the small bomb detonated in the tube causing the explosion. The ammo in question is now being suspended worldwide while the incident is being investigated. Two potential problems. One could have been humor error and the second could have been some sort of mechanical failure where the bomb went off prior to the point where it should have. Reporter: Army depot is located 140 miles southeast of reno and is considered an ideal training facility for special forces preparing to deploy. Reporter: Hundreds of community members gathered to mourn the loss. For those guys to lose their lives the way they did in a training exercise, it was horrible. My heart goes out to them. It's a hard thing no matter what. Reporter: The names of the marines have not been released yet but we have learned their remains will be flown to dover air force base later today and, amy, all the people we talked to last night said all they want are answers so this kind of thing does not have to happen again. Amy. Such a sad story. Abbie boudreau, thank you.

This transcript has been automatically generated and may not be 100% accurate.

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